Polyvinyl acetal resin sheets containing tetrahydrofurfuryl maleate



Patented Dec. 19', 1939 UNlTED STATES PATENT OFFICE POLYVINYL ACETAL RESIN SHEETS CON- TAINING TETRAHYDROFURFURYL MALE- ATE No Drawing. Application October '7, 1938, Serial No. 233,881

3 Claims. -(Cl. 260-36) This invention relates to plastic compositions, and more particularly to compositions comprising a polyvinyl acetal resin and a conditioning agent.

One object of this invention is to produce compositions of matter which may be made into v produce compositions of matter which can be made into sheets suitable for use in laminated, shatter-proof glass. Still another object is to produce compositions which can be rolled, ex.-

- trudecl, molded or otherwise worked into relative- .7 ticizing.

1y thick sheets and massive plastics. A further object is to produce composition". suitable for use in lacquers, artificial silk filaments, wrapping tissues and the like. Other objects will hereinafter appear.

I have discovered that tetrahydrofurfuryl maleate is a very useful conditioning agent for polyvinyl acetal resins. Not only does it serve as a plasticizer in the accepted sense of the term, increasing the flexibility and toughness of polyvinyl acetal resin films, sheets, or other objects or 'masses containing it, but when used in amounts of about 50 or more parts per 100 parts of certain of the polyvinyl acetal resins, namely the polyvinyl acetal resins in which a predominating proportion of the acetal groups are butyraldehyde acetal groups, it has an unusualand remarkable effect which I may call elas- That is to say, a sheet of a polyvinyl butyraldehyde acetal resin containing about 50 or more parts of tetrahydrofurfuryl maleate per 100 parts of resinpossessespthe property which, in the rubberindustry, is known as nerve: namely, theproperty of stretching to a considerable extent when tension is exerted upon it, and returning to its original dimensions when the tension is released. This property renders such 'sheets which I shall call rubbery sheets, particularly useful in the manufacture of shatterproof glass.

For the manufacture of cast films-or sheets, the polyvinyl acetal resin and tetrahydrofuriuryl maleate may be dissolved in a suitable solvent or solvent mixture, such, for instance, as acetone, methanol, acetone-methanol mixtures, ethylene chloride-methanol mixtures, etc., about 300 to 500 or more parts of the solvent or solvent mixmaleate per 100 parts of resin may be employed, depending upon the nature of the resin and the purpose for which the sheets are to be used. Suit-. able proportions of tetrahydrofurfuryl maleate for any resin and any purpose may be readily determined by experiment. For the manufacture of sheets suitable for photographic film base, from 2 to 25 parts of tetrahydrofurfuryl maleate per 100 parts of resin are suitable. The resin solution is cast as a sheet, the solvent evaporated, and the sheet stripped from the casting surface.

Sheets for use in laminated glass may be formed by casting, or may be made without the use of volatile solvent by extrusion,.for example in the manner set forth in application Serial No. 147,934 of John S. Kimble and Ernest C. Blackard, filed June 12, 1937. For instance, 50 or more parts of tetrahydrofurfuryl maleate and 100 parts of a polyvinyl butyraldehyde acetal resin may be mixed in a suitable, jacketed mixer at a low temperature, for example '10 C., on hot rolls, in the manner described in U.,S. Patent 2,048,686 of F. R. Conkl'in, until complete homogenization has taken place. The mass thus produced may then be extruded through an' annular die, and the tube so formed slit to form a sheet.

The polyvinyl acetal resins can be prepared by reacting polyvinyl alcohol with an aldehyde in the presence of an acetal condensation catalyst, e. g. a mineral acid. These resins can also be prepared by simultaneously de-esterifying a poly-- vinyl aliphatic ester and reacting the de-esterification product with an aldehyde in the presence of a de-esterifying catalyst and acetal condensation catalyst. Mineral acids are catalysts for both de-esterification and acetal formation. Among the polyvinyl acetal resins with which tetrahydrofnrfuryl maleate is useful may be men tioned, as illustrative examples, the' polyvinyl formaldehyde acetal resins, the polyvinyl acetaldehyde acetal resins, the polyvinyl formaldehyde acetaldehyde mixed acetal resins, the polyvinyl butyraldehyde acetal resins, and the polyvinyl butyraldehyde acetaldehyde mixed acetal resins.

Examples of the preparation of polyvinyl formaldehyde acetal resins may be found in U. S. Patent 1,955 ,068,-Examples 1, 4 and 5; in U. S.- Patent 2,036,092, Examples 1, 2, 3, 7 and 8; in British Patent 454,691, Examples 1, 2, 3 4, 5, 6 and 7; in British Patent- 404,279, Example 3; and in British Patent 436,072, Examples 1, 2, 3, 4, 5, 6

and 7.

Examples of the preparation of polyvinyl acetaldehyde acetal resins may be found in U. S. Patent 2,044,730, Example 1; U. S. Patent 1,955,068, Example 2; U. S. Patent 2,036,092, Examples 4, 5 and 6; British Patent 466,598, Examples 1, 2, 3, 4 and '7; British Patent 404,279, Examples 1, 2, 4, 5, 6, 7 and 8; U. S. Patent 1,990,399; and French Patent 808,578, Examples 1, 2 and 3.

An additional example of the preparation of a polyvinyl acetaldehyde acetal resin is as follows:

50 lbs. of polyvinyl acetate, the viscosity of whose molar solution in benzene was 45 centipoises, was dissolved in a mixture composed of 50 lbs. of 95% ethyl alcohol and 90 lbs. of ethyl acetate. To this solution was added 19.2 lbs. of paraldehyde. Then a catalyst consisting of 5 lbs. of 95% sulfuric acid diluted with 5 lbs. of water was added. After thorough mixing the reaction was allowed to proceed at 40 C. for 8 days. The reaction mixture was then diluted with acetone, and the resin precipitated by pouring into cold water, washed and dried. Analysis showed the resin to havean acetate group content equivalent to 3.3% of polyvinyl acetate and a hydroxyl group content equivalent to 6.5% of polyvinyl alcohol.

Examples of the preparation of polyvinyl formaldehyde acetaldehyde mixed acetal resins may be found in British Patent 430,136, Examples 1, 2,3, 4, 5 and 6; British Patent 445,565, Exampie 2; British Patent 465,873, Examples 1, 2, 3, 4, 5 and 6; French Patent 808,586, Examples 1, 2, 3, 4, 5, 6, 12, 13, 14, 15, 16, 1'7, 18 and 19.

Additional examples of the preparation of polyvinyl formaldehyde acetaldehyde mixed acetal resins are given in the application of Ralph H. Talbot, Serial No. 85,960, filed June 18, 1936, as follows:

Example 1 100 parts (1.16 mol. calculated as monomeric vinyl acetate) of a polyvinyl acetate (45 centlpoises), 100 parts of ethyl alcohol, 180 parts of ethyl acetate, 34 parts (.77 mol. as monomeric acetaldehyde) of paracetaldehyde and 5.8 parts (.196 mol. as monomeric formaldehyde) of paraformaldehyde were placed in an enamelled vessel and brought into solution by stirring. When solution was complete, parts of sulfuric acid (sp. g'. 1.84) in 10 parts of water were added, and the mixture stirred. The mixture was maintained at a temperature of 40 C. for 144 hours. The contents of the vessel were then diluted with about two and a half volumes of acetone, and the mixture precipitated into water. The precipitated resin was washed free from impurities by repeated changes of cold water, and dried. The

resin, when analyzed, gave a hydroxyl group content equivalent to about 6.4 per cent by weight .of polyvinyl alcohol, an acetate group content equivalent to about 4.0 per cent byweight of polyvinyl acetate, a formaldehyde acetal group content equivalent to about 15.9 per cent by weight'of polyvinyl formaldehyde acetal and an acetaldehyde acetal group content equivalent to Example 2 50 parts (.58 mol. as monomer of polyvinyl acetate centipoises) parts of ethyl alcohol,

90 parts of ethyl acetate, 17 parts (.385 mol. as monomer) of paracetaldehyde, 2.9 parts (.098 mol. as monomer) of paraformaldehyde, 5 parts of sulfuric acid and 5 parts of water were treated as in Example 1 for 161 hours. The well washed and dried resin gave upon analysis a hydroxyl group content equivalent to about 9.6% by weight of polyvinyl alcohol, an acetate group content equivalent to about 4.1% by weight of polyvinyl acetate, a, formaldehyde acetalgroup content equivalent to about 13.9 per cent by weight of polyvinyl formaldehyde acetal, and an acetaldehyde acetal group content equivalent to about 69.9 per cent of polyvinyl acetaldehyde acetal. The polyvinyl acetal portion of the resin was therefore made up of about 18.5 percent by moles of polyvinyl formaldehyde acetal and 81.5 per cent by moles of polyvinyl acetaldehyde acetal. The resin was soluble in acetone to an extent which permitted coating a film or sheet from the resin.

Example 3 1300 parts (15.1 mol. as monomer) of a polyvinyl acetate (45 centipoises), 1700 parts of ethyl acetate, 2250 parts of ethyl alcohol (95%) and 48 parts (1.57 mol. as monomer) of paraformaldehyde (trioxymethylene) were placed in a vessel equipped with a reflux condenser and a means of agitation, and the contents brought to a temperature of about C. by means of steam heating. 182.25 parts of sulfuric acid (sp. g. 1.84) dissolved in 51.5 parts of water were added, and the whole was heated at about 70 C. for about five hours, agitating throughout. At this point, 266.4 parts (6.05 mol. as monomer) of paracetaldehyde were added and heating at about 70 C. with agitation was continued for a further period of twenty hours. The contents of the reaction vessel were neutralized with ammonium hydroxide and diluted with water precipitating the resin as a cake. The cake was cut into small pieces and repeatedly washed with hot water until the resin was free from solvents, salts and other impurities. The resin, upon analysis, showed a hydroxyl group content equivalent to about 10.1 per cent by weight of polyvinyl'alcohol, an acetate group content equivalent to about 3.2 per cent by weight of polyvinyl acetate, the remainder of the weight of the resin being polyvinyl acetal. The polyvinyl acetal portion of the resin was made .up of about per cent by moles of polyvinyl acetaldehyde acetal and about 20 percent by moles of polyvinyl formaldehyde acetal. The resin was not quite soluble in acetone, but could be made to dissolve by admixing small amounts or other solvents, such as alcohols, with the acetone.

Examples of the preparation of polyvinyl butyraldehyde acetal resins may be found in U. 8. Patent 2,044,730, Examples 2, 5 and 6; British Patent 466,598, Example 5; French Patent 813,- 303, xample 1; French Patent 813,514, Examples 1, 2, 3, and 4; and British Patent 459,878, Examples 1, 2, 5, 6, 7, 8, 9 and 10.

Additional examples of the preparation of polyvinyl butyraldehyde acetal resins are as follows:

20 lbs. of polyvinyl acetate, the viscosity of whose molar solution in benzene was 45 centipoises, was dissolved in 20 lbs. of ethyl alcohol and 36 lbs. of ethyl acetate. To this solution was added 13 lbs. of butyraldehyde and a solution of 2 lbs. of sulfuric acid in 2 lbs. of water. The reaction mixture was allowed to stand for 8 days at 40 C., after which it was diluted with acetone water, washed and dried. Analysis showed the resin to have an acetate group content equivalent 1 to 7.8% by weight of polyvinyl acetate and a hydroxyl group content equivalent to 4.8% by weight of polyvinyl alcohol.

23.6 lbs. of polyvinyl acetate, the viscosity of. whose molar solution in benzene was 45 centipoises, was dissolved in 56.5 lbs. of 95% ethyl alcohol. .To this solution was added 7.9 lbs. of butyraldehyde and 5.9 lbs. or HCl. The reaction mixture was allowed to stand for 4 days at C., after which it was diluted with ethyl alcohol and acetic acid, and the resin precipitated by pouring into cold water, washed, and dried. Analysis showed the resin to have an acetate group content equivalent to 3.1% by weight of polyvinyl acetate and a hydroxyl group content equivalent to 16.3% by weight of polyvinyl alcohol.

An example of the preparation of a polyvinyl.

butyraldehyde acetaldehyde mixed acetal resin is given in French Patent 813,303, Example 2.

. ing its transparency.

What I claim as my invention and desire to be secured by Letters Patent 01 the United States is;

1. A transparent, rubbery sheet comprising 100 parts of a polyvinyl acetal resin in which a predominating proportion of the acetal groups are butyraldehyde acetal groups, and at least parts, approximately, of tetrahydrofurturyl maleate as an elasticizer therefor.

2. A transparent, rubbery sheet comprising parts of a polyvinyl butyraldehyde acetal resin and at least 50 parts, approximately, of tetrahydrofurfuryl maleate as an elasticizer therefor.

3. A transparent, rubbery sheet comprising a polyvinyl acetal resin in which a predominating proportion of the acetal groups are butyraldehyde acetal groups, and anamount of tetrahydroiurturyl maleate sumcient to impart to the sheet a rubbery character without substantially impair- HENRY B. SMITH. 

